118 research outputs found
Interfering resonances in a quantum billiard
We present a method for numerically obtaining the positions, widths and
wavefunctions of resonance states in a two dimensional billiard connected to a
waveguide. For a rectangular billiard, we study the dynamics of three resonance
poles lying separated from the other ones. As a function of increasing coupling
strength between the waveguide and the billiard two of the states become
trapped while the width of the third one continues to increase for all coupling
strengths. This behavior of the resonance poles is reflected in the time delay
function which can be studied experimentally.Comment: 2 pages, 3 figure
Update on Bone Grafting Materials Used in Dentistry in the Bone Healing Process: Our Experience from Translational Studies to Their Clinical Use
The use of bone grafts is important to preserve the alveolar bone ridge height and volume indispensable for dental implant placement. Despite the highly successful outcomes for the implant-supported overdentures, it seems that a majority of edentulous individuals have not pursued implant-based rehabilitation. Among the reasons cited for this, discrepancy between highly successful therapy and its acceptance is the cost of the treatment. Therefore, the development of biomaterials for bone grafting with comparable characteristics and biological effects than those renowned internationally is necessary. In addition, domestic manufacture would reduce the high costs in public health arising from the application of these biomaterials in the dental field. The aim of the following chapter is to offer an update on one bone grafting material frequently used in dentistry through an assessment of anorganic bovine bone graft in small and medium experimental models as well as its clinical use
Angular momentum dependence of the GDR width in Sn nuclei at fixed excitation energy
Abstract High-energy γ-rays from the decay of the giant-dipole resonance (GDR) in the hot 106Sn compound nucleus and its daughters were measured in coincidence with heavy recoiling evaporation residues. The compound nucleus was formed at excitation energy E ∗ = 80 MeV using the reaction 56Ni+48Ti at a bombarding energy of 260 MeV. The analysis yields the GDR width for two different intervals of angular momentum 〈J〉 = 24 and 36ℏ. The present data, combined with previous data at higher angular momentum permit a study of the angular momentum dependence of the GDR width for 10 ⩽ J ⩽ 60ℏ at approximately fixed temperature. The width of the GDR is found to be roughly constant for
GDR in Superdeformed Nuclei
A search for the gamma decay of the Giant Dipole Resonance built on superdeformed nuclear configurations was made. The superdeformed states of the Eu-143 nucleus were populated using the reaction Pd-110(Cl-37, 4n)Eu-143 at a beam energy of 165 MeV. High energy gamma-rays were detected in 8 large BaF2 scintillators in coincidence with discrete transitions measured with part of the NORDBALL array (17 HPGe detectors and a 2 pi multiplicity filter). Spectra of high-energy gamma-rays gated by low-energy transitions from states fed by the superdeformed bands show an excess yield in the 7-10 MeV region with respect to those gated by transitions from states not populated by the superdeformed bands. Because the dipole oscillation along the superdeformed axis of the nucleus is expected to have a frequency corresponding to approximate to 8 MeV (low energy component of the GDR strength function), the present result gives the first experimental indication of gamma-ray emission of the GDR built on a superdeformed states
The damping width of giant dipole resonances of cold and hot nuclei: a macroscopic model
A phenomenological macroscopic model of the Giant Dipole Resonance (GDR)
damping width of cold- and hot-nuclei with ground-state spherical and
near-spherical shapes is developed. The model is based on a generalized Fermi
Liquid model which takes into account the nuclear surface dynamics. The
temperature dependence of the GDR damping width is accounted for in terms of
surface- and volume-components. Parameter-free expressions for the damping
width and the effective deformation are obtained. The model is validated with
GDR measurements of the following nuclides, K, Ca, Sc,
Cu, Sn,Eu, Hg, and Pb, and is
compared with the predictions of other models.Comment: 10 pages, 5 figure
Possible Conservation of the K -Quantum Number in Excited Rotating Nuclei
The \ensuremath{\gamma} cascades feeding into low-K and high-K bands in Er are investigated analyzing variances and covariance of the spectrum fluctuations. From a large data set of 1 triple coincidences, \ensuremath{\gamma}-\ensuremath{\gamma} coincidence spectra gated by resolved low-lying rotational bands are analyzed. Low-K bands are found to be fed by a much larger effective number of cascades than high-K bands. The covariance between pairs of gated spectra shows that the cascades feeding low-K bands are different from those feeding the high-K bands. The persistence of the K-selection rules for the excited rotational bands within the angular momentum region 30\ensuremath{\Elzxh}\ensuremath{\le}I\ensuremath{\le}40\ensuremath{\Elzxh} is suggested as explanation
Critical behavior in the variation of GDR width at low temperature
We present the first experimental giant dipole resonance (GDR) width
systematics, in the temperature region 0.8 1.2 MeV for Tl, a
near Pb nucleus, to investigate the evolution of the GDR width in shell effect
& pairing dominated region. The extracted GDR widths are well below the
predictions of shell effect corrected thermal shape fluctuation model (TSFM)
and thermal pairing included phonon damping model. A similar behavior of the
GDR width is also observed for Cu measured in the present work and
Sb, measured earlier. This discrepancy is attributed to the GDR induced
quadrupole moment leading to a critical point in the increase of the GDR width
with temperature. We incorporate this novel idea in the phenomenological
description based on the TSFM for a better understanding of the GDR width
systematics for the entire range of mass, spin and temperature.Comment: Accepted for publication in Phys. Lett. B, 7 pages, 4 figure
Scaling Properties of the Giant Dipole Resonance Width in Hot Rotating nuclei
We study the systematics of the giant dipole resonance width in hot
rotating nuclei as a function of temperature , spin and mass . We
compare available experimental results with theoretical calculations that
include thermal shape fluctuations in nuclei ranging from A=45 to A=208. Using
the appropriate scaled variables, we find a simple phenomenological function
which approximates the global behavior of the giant dipole
resonance width in the liquid drop model. We reanalyze recent experimental and
theoretical results for the resonance width in Sn isotopes and Pb.Comment: LaTeX, 4 pages with 4 figures (to appear in Phys. Rev. Lett.
Compilation of Giant Electric Dipole Resonances Built on Excited States
Giant Electric Dipole Resonance (GDR) parameters for gamma decay to excited
states with finite spin and temperature are compiled. Over 100 original works
have been reviewed and from some 70 of which more than 300 parameter sets of
hot GDR parameters for different isotopes, excitation energies, and spin
regions have been extracted. All parameter sets have been brought onto a common
footing by calculating the equivalent Lorentzian parameters. The current
compilation is complementary to an earlier compilation by Samuel S. Dietrich
and Barry L. Berman (At. Data Nucl. Data Tables 38(1988)199-338) on
ground-state photo-neutron and photo-absorption cross sections and their
Lorentzian parameters. A comparison of the two may help shed light on the
evolution of GDR parameters with temperature and spin. The present compilation
is current as of January 2006.Comment: 31 pages including 1 tabl
Proposta di una “checklist” per il prelievo di sangue venoso
The collection of venous blood is central in clinical laboratory activity. Although there is widespread perception that this practice is simple and free of complications and side effects, it is undeniable that the vast majority of laboratory errors arises from ignorance, incompetence or negligence during venipuncture. It has hence become advisable to prepare a document in simplified form of checklist, consisting of a concise but comprehensive list of activities to be completed or verified in order to prevent errors during venous blood collection. In the intention of authors, this synthetic checklist is a modular tool, adaptable to different local contexts, it can be easily and gradually implemented, it is supported by scientific evidence and consensus of experts and created with the support of different healthcare professionals and it is adherent to the best practices and requires minimal resources for implementation. It is reasonable to assume that this checklist may be able to withstand system and individual changes, strengthening the standards for safety of both operators and patients, limiting potential failure patterns. We hope that the checklist may be implemented in all healthcare facilities where routine venous blood collection is performed, after adaptation to suit characteristics of local organization
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